Link Not Validating - Can't Save Link, but Webpage I'm Linking to Loads Fine

I've been trying to add a link to http://happyearthtea.com/ in my page on high caffeine teas.  It keeps giving me an error, saying the link won't validate.  I first tried linking to a specific page on this site, then to the homepage, but neither works.  Meanwhile, the site itself loads just fine and doesn't even show much of a slowdown.

Is there anything I can do about this?  I'd really like to include a live link to this site, as I recommend one of their teas on this page, but I don't know if there's any way I can do this without someone manually fixing something.

Thanks!

I tried it myself without success. Even checked HTML.

So I wrote to Simon for help.

I wish so much, I had a solution at hands! Unfortunately, our link validator fails on a few hosts - and apparently, this one is among them. Despite efforts, we couldn't find a a work around so far ... I'll talk to Hans right now ...

Thanks!

I've run into stuff like this on my server.  I think some servers actually have pretty sophisticated filters in place to detect and block certain types of bots, probably for security and traffic reasons.  There are several scripts I have written that attempt to crawl external pages, to validate things.

Sometimes I've been able to change the request headers, like how the server identifies itself when it makes the request...but this is a complex guessing game and it's not always successful.  Much of the time I've had to result to checking certain cases manually.

I just tried again, and now it works fine with http://happyearthtea.com/ ... Just thought I'd let you know.